Simulation is used to: (1) verify that newly developed algorithms are computationally correct, (2) test the validity of newly developed methods of genetic segregation and linkage analysis and investigate the statistical properties of the test statistics, (3) determine the power and robustness of these methods when analytic methods are intractable, and (4) apply insights gained from these simulation experiments to the collaborative research projects. In the past year the simulation program has been used to determine the appropriate number of degrees of freedom for the model-free sib-pair linkage test incorporating half-sibship data, to determine the statistical validity of this test under two different null hypotheses, and to determine the power of the sib-pair test with highly polymorphic markers. Currently a completely new program is being written that will simulate data under any model that is available in the S.A.G.E. program package.